It is known that LiAlH.sub.4, AlH.sub.3, and NaAlH.sub.4 are effective reducing agents for a number of organic compounds. See for example U.S. Pat. Nos. 4,006,095, and 3,926,833. However if the organic compound is a halogenated organosilicon compound, by-product AlCl.sub.3 thus produced can catalyze dismutation (Si-C cleavage) of the hydrides that are formed. Additionally, AlCl.sub.3 can induce polymerization or isomerization when reducing alkenylchlorosilanes. Consequently, the reaction mixture may have to be hydrolyzed, or the hydride extracted from the reaction solution with petroleum ether before fractionation in order to obtain the desired product.
Organosilanes are useful in the production of tetraalkysilanes which in turn are suitable for use in formulating hydraulic fluids and lubricants which are stable at high temperatures. One means of converting organosilanes to tetraalkylsilanes suitable for use in the formulation of hydraulic fluids and lubricants stable at high temperatures is described in U.S. Pat. No. 4,595,777, the disclosure of which is incorporated herein by reference. Organosilanes are also useful in the formation of polymethylhydrosiloxanes which in turn are useful in the textile industry to waterproof and improve the wear resistance of fabrics.
The reaction of organohalosilanes with metal hydrides such as LiAlH.sub.4, and NaAlH.sub.4, is usually conducted in an anhydrous solvent such as diethyl ether, tetrahydrofuran, diglyme, or dioxane because of the low solubility of the metal hydride in liquid hydrocarbon media. The extent and efficiency of the reaction is dependant on intimate contact of the reactants, hence solubility of the reducing agent is an important consideration.
Of the reducing agents, AlH.sub.3 is known to be a selective hydrogenating and reducing agent for various organic reactions. One method of producing AlH.sub.3 is a two step procedure, starting with LiH, wherein the latter is initially reacted with AlCl.sub.3 in the presence of certain ethers, notably, diethylether, to produce lithium tetrahydridoaluminate or lithium aluminum hydride (LiAlH.sub.4), and the latter is then reacted with AlCl.sub.3 in the presence of ether, usually diethylether. Unfortunately, solutions of AlH.sub.3 are quite unstable in ethers. See for example, U.S. Pat. No. 4,006,095.
Alkali metal hydrides, such as NaH or LiH have also been used to reduce organosilicon halides to the hydrides, however high temperatures are usually required (e.g., 200.degree.-300.degree. C.) and the hydrides are often produced in low yields. In the case of alkali metal hydrides, polar solvents such as hexamethylphosphoric triamide or tetramethylurea are required.
Not all chlorosilanes can be reduced successfully using NaH in ether solvents. Dimethyldichlorosilane is not reduced by NaH even on prolonged refluxing in dioxane. See Charles H. Van Dyke "The Bond to Halogens and Halogenoids," Marcel Dekker, Inc. N.Y., 1972, pp. 234-240. Nevertheless, the use of alkali metal hydrides does avoid the formation of AlCl.sub.3 which has the disadvantages noted previously.